In order to increase braking power it is known to increase the surface area of friction material (eg brake pads or brake shoes) for pressing against a rotating body. For example, on heavy vehicles present practice is to use brake drums with brake shoes. Brake drums are known to have certain advantages over disc brakes. Major advantage of drum brake over disc brake is the superior braking force in some situations such as the continued application of braking force where temperature variations occur while the brake is on. However drum brake assemblies are complex in construction and assembly and generally comprise a large number of components and parts. As a result of the large number of components the brake assembly is expensive and time consuming to both assemble and to mount the brake system on the vehicle.
A further problem with drum brakes is that the drum shoe brake linings often do not become properly bedded in by wearing against the inner surface of the drum. To achieve good results a near perfect match is required between the diameters of the friction lining and the brake drum when the brake is applied. If the brake shoe lining is not in a proper contact with the brake drum over its entire surface it will result in an inferior or diminished braking force.
In relation to vehicles with disc brakes in order to improve braking power, it is possible to mount for example two sets of callipers about a rotating disc. An alternate method is to employ multiple discs which rotate with but are able to slide axially along a rotating body such as an axle and which are interleaved with fixed discs of friction material. In these multi-disc systems, an actuator such as a piston applies an axial force on the discs, causing them to press against the friction material and thus provide a braking effect.
While both the above methods for increasing braking power achieve their desired effect, they are not without disadvantage. For example, the area taken up by a brake calliper is relatively large compared to the area of brake pad that the calliper can apply to a disc. Therefore there is an inherent inefficiency in terms of the number of callipers that can be applied about a disc compared to the actual area of brake pad/disc contact. Further, there are inherent space limitations in conventional vehicles which prohibit the mounting of multiple callipers about a disc. With reference to the abovementioned multi-disc systems, these are relatively complex systems and also take up a substantial space which is often not available in production vehicles.